core: fix graceful stop (#4866)

core: fix graceful stop (#4865)

* core/grpc: fix graceful stop

* core/http: add graceful stop serve

Co-authored-by: Caleb Doxsey <cdoxsey@pomerium.com>

pkg/contextutil/contextutil.go

@@ -64,3 +64,25 @@ func (mc *mergedCtx) Value(key interface{}) interface{} {
 	}
 	return mc.doneCtx.Value(key)
 }
+
+type onlyValues struct {
+	context.Context
+}
+
+// OnlyValues returns a derived context that removes deadlines and cancellation,
+// but keeps values.
+func OnlyValues(ctx context.Context) context.Context {
+	return onlyValues{ctx}
+}
+
+func (o onlyValues) Deadline() (time.Time, bool) {
+	return time.Time{}, false
+}
+
+func (o onlyValues) Done() <-chan struct{} {
+	return nil
+}
+
+func (o onlyValues) Err() error {
+	return nil
+}